Means for detecting sounds.



D. MCLENNAN.

mums FOR 0512mm sounms.

APPLICATWN FILED OCT-13,1917.

Patentsd; Mar. 11', 191%.

DUNCAN MCLENNAN, OF CROYDON, ENGLAND.

MEANS FOR DETECTING SOUNDS.

Specification of Letters Patent.

Patented Mar. 11., 1919.

Application filed October 13. 1917. Serial No. 196,548.

To all whom it may oncern.

Be it known that I, Dr'xcax McLnxxax. a subject of the King of GreatBritain and Ireland, residii'ig at Croydon, in the county of Surrey,England, have invented Improvements in ll leans for Detecting Sounds.ot' which the following is a speciti 'ation.

This invention relates to compound diaphrag'ms for use in or withsomul-trans n'iitt-ing and s m1ul-receiving instruments or apparatussuch as telephones phonographs, stethoscopes, signaling instruments andthe like.-

A compound diaphragm arrangement according to the present inventioncomprises coaxial diaphragms mounted parallel to one another so astoform between them a closed space that is charged with liquid, thediaphragms being of different effective diameters and maintained apartat their peripheries by interposed peripheral distance pieces so toinsure their being kept parallel one to= another, the central portion ofthe closed space between them being always free except for the containedliquid. More than two diaphragms may be thus arranged to form two ormore spaces that are filled with liquid. With such an arrangement, thevibrations are rendered dead-beat by the liquid. Furthermore, when thetwo or several diapl'iragms are of different sections or thicknesses,and therefore of different periodicity values, the range of notes towhich the combination will respond is considerably augmented.

Such a compound diaphragm arrangement with parallel diaphragzms andinter posed liquid, may be cmploytal generally in or withsoimd-transmittino and soundreceiving instruments or apparatus.

The distance or distances between. the elementary diaphragms should besmall compared with the diameters of the diaphragms or at least comparedwith the diameter oi the larger or largest diaphragm it the diaphragmsditi'er greatly in diameter.

hen this compound or combination diaphragm arrangement is applied say toa telephone transmitter. the microphone would be attached to one sideand the air vibrations or waves caused by the voice would act on theother side.

Similarly, in the case of say a telephone receiver, the magnet poleswould l applied to one side of the combination diaphragm a d thelisteners ear placed near the other.

Any suitable liquid may be used between the diaphragms. A liquidsuitabletor the purpose is a. mixture of distilled water and glycerin.

In the accompanying drawings, Figure l is a face VlCW and Fig. 2 asection on the line 2; of Fig. 1 showing: one example of a compounddiaphragm arrangement having elementary diaphragrms ot' ditterentctt'ective diameters with liquid chamber according to the invention.Figs. 3 and are similar views of another example o't'.a compountdiaphragm according to the invention.

The compound diaphragm arrangement. shown in Figs. l and 2 comprises twocircular metal diaphragms a and o secured to the opposite sides of aring 0 recessed so that the efi'ective portions of the two diaphragmssecured to its opposite sides are in ett'ect of different diameters forthe purpose hereinbefore explained. The ring may be of any suitablematerial, metallic or non-metallic, for example vulcanite, so as to formtherewith a closed chamber that is charged with liquid (ll. For thelatter purpose the ring 0 may also be formed with two oppositelyarranged holes 0 and f for exit of air and inlet of the liquid. theseholes being afterward hermetically closed, as for instance by screws g,or caps. In this example the two diapliraems a and I) are shown as ofunequal thickness.

The closed chamber may be completely tilled with liquid or only partlytilled. When the ring (2 is of metal the diaphrae'n'is a and 7) may besecured thereto in a tluid tight manner as by soldering the partstogether, or in any case the diaphragn'is and interposed ring, whetherof metal or other material, may be clamped together bet-Ween outer ringsa, as by screws passing through the assembled parts.

in the compound diaphragm arrangement shown in 3 and 4 there are threediaphragms a, 7) and I1 clamped in place within a holderz' by rings j,and m respectively which may be. screwed into the holder '11, as shown,in be otherwise held together so as to form two interposed chamberscharged with liquid (Z.

As will be readily undcrstoml, compound diaphragm arrangements such asdescribed can be used in ('(JlliltttlOl'l with apparatus of variouskinds, some of which have hereinbetore been indicated, designed for thetrans mission, reproduction or detection of sounds,

olccta'iouliy or otherwise. One ugpiication of s11 a sompoxmd dtuphz'agm uri'amgvnzont is; cribud in the :spocii Lion of anotherapplication for otters Pun-m mod (13th @miobcr 1917) by me ("MLifll No.2965 or uso in common! ioo with sound dmovting upprv mtus. @Hmi useswill brrozuiiLy understood Without further oxplzumiion.

11M (whom is1--- 1. A. sound hmmniffing or wwiving compound dinphm =11ommgrising: (Uuphrugms zuirungod in 211103 to (nu-n other, moans foruonneoting tho poi'iphvl'ul portions of said diaphmgms and liquidinclosod Within the space im'n'md by said dinphmg'ms the pox tion of {hedizxphrngms oxnosod to the liquid being; of difi'omnt vfi'eci'ivo arm.

A sound 'nwmsmii'iiing 0! receiving; compound diaphragm uompl'isingfilamentary diaphragxns 1110:1115 of (HEM-on! Miami: widti'xs e-ximidingilm'm'dly from 131c com mon pvriphmios of and iv f om with said 9 ommfim ans vori'esponm 7 effoofive diameters ,0 his )h 1155 and forming a andliquid imiosod Within he an id :liupm'agm snbsmn! izaily as 3. sounnmnsmitt pound diaphz z wherein the 01 nnoqunl 'thioim A compound din asclaimed in claim us with info hem portums mil-s of between r asdoscribeo.

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